\
.\" This man page was generated by the Netpbm tool 'makeman' from HTML source.
.\" Do not hand-hack it!  If you have bug fixes or improvements, please find
.\" the corresponding HTML page on the Netpbm website, generate a patch
.\" against that, and send it to the Netpbm maintainer.
.TH "Pamsummcol User Manual" 0 "25 January 2009" "netpbm documentation"

.SH NAME
pamsummcol - summarize (sum, average, etc) a Netpbm image by column

.UN synopsis
.SH SYNOPSIS
\fBpamsummcol\fP
{
\fB-sum\fP |
\fB-mean\fP |
\fB-min\fP |
\fB-max\fP
}
[\fIimagefile\fP]
.PP
All options can be abbreviated to their shortest unique prefix.
You may use two hyphens instead of one.  You may separate an option
name and its value with white space instead of an equals sign.

.UN description
.SH DESCRIPTION
.PP
This program is part of
.BR Netpbm (1)
.
.PP
\fBpamsummcol\fP reads a Netpbm image (PNM or PAM) and performs a
summary function over all the rows in each column (sum, mean, etc.).
It produces an image of the same kind that the same width and depth as
the input, and one row high.  Its sample values are the result of the
summary.
.PP
\fBpamsummcol\fP performs the summary operation on each plane
independently.
.PP
\fBpamsummcol\fP performs the operation on the actual sample values,
not on the light intensities represented by them in the case that the
image is a PGM or PPM image.
.PP
If you want to summarize by row instead of by column, run the input
through \fBpamflip\fP first (and if you want the output to be a single
column instead of a single row, use \fBpamflip\fP again).
.PP
If you want to summarize over the entire image (getting a one-tuple
output image), use \fBpamsumm\fP to get a summary row, \fBpamflip\fP
to turn that into a column, the \fBpamsumm\fP again to summarize the
column.
.PP
If you want to summarize the individual samples in an entire image,
instead of by tuple, use \fBpamsumm\fP.
.PP
\fBpamsummcol\fP performs the operation on the actual sample values,
not on the light intensities represented by them in the case that the
image is a PGM or PPM image or PAM equivalent.  You can use
\fBpnmgamma\fP to convert such an image to one with samples proportional
to light intensity, and then use \fBpamsummcol\fP on the result.
.PP
You can achieve the same thing as \fBpamsummcol -mean\fP with
\fBpamscale\fP.  Just scale vertically to a single row, without scaling
horizontally at all.  Use the pixel mixing method.


.UN options
.SH OPTIONS
.PP
You must specify exactly one of \fB-sum\fP, \fB-mean\fP,
\fB-min\fP, or \fB-max\fP.


.TP
\fB-sum\fP
.sp
This option makes the summary function addition.
     In each column and plane of the output row, the sample value is the
     sum of all the samples values in the same column and plane of the input.
     If a result is greater than the image maxval, it is clipped to
     the maxval.

.TP
\fB-mean\fP
.sp
This option makes the summary function arithmetic mean.
     In each column and plane of the output row, the sample value is the
     mean of all the samples values in the same column and plane of the input.

.TP
\fB-min\fP
.sp
This option makes the summary function arithmetic minimum.
     In each column and plane of the output row, the sample value is the
     minimum of all the samples values in the same column and plane of
     the input.

.TP
\fB-max\fP
.sp
This option makes the summary function arithmetic maximum.
     In each column and plane of the output row, the sample value is
     the maximum of all the samples values in the same column and
     plane of the input.



.UN seealso
.SH SEE ALSO
.BR pamsumm (1)
,
.BR pamscale (1)
,
.BR pamfunc (1)
,
.BR pamarith (1)
,
.BR pamscale (1)
,
.BR pam (5)
,

.UN history
.SH HISTORY
.PP
\fBpamsummcol\fP was added to Netpbm in Release 10.21 (March
2004).